1. The Field of the Invention
The present invention relates to fluid mixing systems and, more specifically, fluid mixing systems having a flexible drive line and/or an impeller having pivotable blades.
2. The Relevant Technology
The biopharmaceutical industry uses a broad range of mixing systems for a variety of processes such as in the preparation of media and buffers and in the growing, mixing and suspension of cells and microorganisms. Some conventional mixing systems, including bioreactors and fermentors, comprise a flexible bag disposed within a rigid support housing. An impeller is disposed within the flexible bag and is coupled with the drive shaft. Rotation of the drive shaft and impeller facilitates mixing and/or suspension of the fluid contained within the flexible bag.
Although the current mixing systems are useful, they have some limitations. For example, where the drive shaft is secured within the flexible bag during the manufacturing process, the rigid drive shaft limits the ability to collapse or fold the flexible bag so as to reduce its size for transportation, storage and/or further processing. Likewise, where it is intended to reuse the drive shaft, such as when it is made of metal, this system has the disadvantage of needing to clean and sterilize the drive shaft between different uses.
In an alternative conventional system, a rotatable tube extends into the flexible bag and has an impeller coupled at the end thereof. During use, the rigid drive shaft is passed down into the tube and couples with the impeller. In turn, rotation of the drive shaft facilitates rotation of the impeller for mixing the fluid within the flexible bag. In this design, with the drive shaft removed, the flexible bag with tube can be folded for ease of storage and transportation. In addition, because the drive shaft does not directly contact the fluid within the bag, the drive shaft does not need to be cleaned or sterilized between uses.
However, the flexible bag is typically secured within the support housing prior to insertion of the drive shaft. It is thus necessary during use to vertically position the drive shaft over the top of the bag for insertion into the tube. For large bags or elongated bags that require a long drive shaft, this can be difficult to accomplish. Furthermore, in situations where the mixing system is located in a room with a relatively low ceiling, it may be impossible to vertically lift the drive shaft over the bag. This type of system also requires increased training in user operation to ensure that the drive shaft is properly received within the tube and properly engaged with the impeller so that the system operates as intended.
Conventional systems also have the drawback that the rigid impellers located within the bags limit the extent to which the bags can be collapsed by folding or other manipulation. Likewise, there are potential concerns that the blades of the impellers can puncture or otherwise damage the bags when the bags are folded around the impeller. In addition, folding the bag around the impeller can place unwanted stress on the rigid impeller blades.
Accordingly, what is needed in the art are mixing systems that solve all or some of the above problems.